The invention was motivated by a series of articles in national newspapers including The New York Times and The Wall Street Journal in the mid 1980's about the difficulties of adequately screening millions of cervical Pap smears every year, resulting in the deaths of many women from cervical cancer. Others have responded to these same articles by developing automated Pap smear screening systems. Law makers have responded to these articles by mandating that the quality of the work performed by cytotechnicians in cytology screening laboratories should be assured.
As the performance of automated Pap smear screening systems improves and their use becomes widespread as a means of cost containment, it becomes increasingly important to periodically confirm that the machines are doing a good job. Periodic checking, rather than verification only at the time of machine type acceptance by the medical community, is necessary because the image processing algorithms will be updated over time and because the machines have many operational variables that affect their performance. An image digitization system as simple as a facsimile machine cannot produce the same digitized image twice, and a Pap smear screening system is far more complex, having to recognize the complex images it digitizes.
What is needed are comprehensive, standard sets of test images that can be periodically scanned by all of the machines. Subtle differences in the specimens that represent the extremes of laboratory practice in obtaining and preparing the specimens should be captured. Until the machines take over, cytotechnicians must be periodically requalified. Since the machines scan specimens on microscope slides, the test images must appear to be natural images and must be handled like natural images--they should be inserted into a batch of specimens without any change to the work flow. Since there may be many machines and cytotechnicians, and since test specimens may be broken during handling, many like copies of the test images must be produced.
By practicing the invention described herein, multiple specimen images can be combined and reproduced life-size to satisfy these requirements. Images with varying brightness and contrast can be made to test equipment behavior with poor quality specimens or lighting. Life-size images of any type of specimen can be provided--the technique is not restricted to Pap smear images. One can also synthesize images to simulate situations that rarely occur in nature, or to simulate situations that occur but for which no specimen is available.